[PyMOL] Chi torsion angles measurements on multiple structures

[Baptiste L. <bap...@gm...>]

Dear all,

I wounder to know about possible ways to measure chi1, chi2 dihedral 
angles on a set of structures. For example, I opened 10 pdb files and 
the phi_psi command allows us to easily obtain the phi and psi values:
Ex: To obtain the phi and psi values of the residue 288 of the chain A 
in the 10 structures,

 >phi_psi ///A/288

  PHE-288:  (  -63.4,  -25.1 )
  PHE-288:  (  -60.1,  -35.9 )
  PHE-288:  (  -65.0,  -28.1 )
  PHE-288:  (  -59.4,  -31.0 )
  PHE-288:  (  -62.6,  -34.7 )
  PHE-288:  (  -80.5,  -36.4 )
  PHE-288:  (  -63.5,  -24.7 )
  PHE-288:  (  -60.5,  -31.7 )
  PHE-288:  (  -63.3,  -38.5 )
  PHE-288:  (  -62.5,  -35.2 )
Then, I tried to get the chi1 and chi2 values for the Phe288. It works 
for a single structure but not for the entire set (e.g. chi1),

 >get_dihedral ///A/288/N, ///A/288/CA, ///A/288/CB, ///A/288/CG

PyMOL>get_dihedral ///A/288/N, ///A/288/CA, ///A/288/CB, ///A/288/CG
GetDihedral-Error: Selection 1 doesn't contain a single atom/vertex.
GetDihedral-Error: Selection 2 doesn't contain a single atom/vertex.
GetDihedral-Error: Selection 3 doesn't contain a single atom/vertex.
GetDihedral-Error: Selection 4 doesn't contain a single atom/vertex.
  cmd.get_dihedral: -1.000 degrees.

Is there a simple way to obtain the same results than for phi and psi, 
may be tuning the phi_psi command...

Thanks for your help,
Best,

Baptiste